[simpits-tech] Mask pressure - a ballpark

[Joseph Fagner]

I bet you're right about the gradient.  If we take a mean arterial blood
pressure of around 110 mmHg, that correlates to about 2.1 psi.  If you want
to actually push blood away from the extremities, then you need to be above
the MAP, so 3.1 would sound about right.

Jay

-----Original Message-----
From: simpits-tech-bounces at simpits.org
[mailto:simpits-tech-bounces at simpits.org] On Behalf Of Brian Sikkema
Sent: Monday, April 02, 2007 5:41 PM
To: simpits-tech at simpits.org
Subject: [simpits-tech] Mask pressure - a ballpark

http://archives.sensorsmag.com/articles/0402/59/main.shtml

This article is talking about a G-sensitive
regulator, the CRU-103. This is what it has to say:

"In operation, the bellows are typically triggered at
3.5 g's, releasing oxygen under pressure at 0.1 psi.
Supply pressure increases gradually to 1.0 psi at 9 g's."

I believe the 0.1 psi and 1.0 psi are actually a
pressure DIFFERENTIAL, meaning it would be that much
over ambient. Anything under 3.5 g's and you'd just
be breathing air at ambient pressure.

That makes a lot of sense, when you think about it.
For those of you who haven't had the pleasure of
breathing through one of these regulators in real
life, when the regulator is in "normal" mode (as
opposed to emergency - the pressure breathing
setting) it's basically just like breathing
regularly. If your hose wasn't connected to anything
at all, that would be what it's like. Because in our
sims, that's exactly how they work it - the hoses
just don't connect to anything.

It's only when you get into the emergency setting
that you get pressure breathing. Here things get
whacky, as you have to actively exhale and passively
inhale - the exact opposite of normal breathing.

Anyway right now if I had to take a guess I'd say
that emergency pressure is probably around 1.0 psi
above ambient. I'll let you know if I find out
differently tomorrow.

Brian

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